{"id":2230834,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2230834/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260430054906.94431-2-amachhiw@linux.ibm.com/","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/1.1/projects/2/?format=json","name":"Linux PPC development","link_name":"linuxppc-dev","list_id":"linuxppc-dev.lists.ozlabs.org","list_email":"linuxppc-dev@lists.ozlabs.org","web_url":"https://github.com/linuxppc/wiki/wiki","scm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git","webscm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/"},"msgid":"<20260430054906.94431-2-amachhiw@linux.ibm.com>","date":"2026-04-30T05:49:00","name":"[1/6] KVM: PPC: Book3S HV: Validate arch_compat against host compatibility mode","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"c398a4528e90c98596f5d53528352ed2232b0a42","submitter":{"id":87864,"url":"http://patchwork.ozlabs.org/api/1.1/people/87864/?format=json","name":"Amit Machhiwal","email":"amachhiw@linux.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260430054906.94431-2-amachhiw@linux.ibm.com/mbox/","series":[{"id":502205,"url":"http://patchwork.ozlabs.org/api/1.1/series/502205/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=502205","date":"2026-04-30T05:48:59","name":"KVM: PPC: Handle CPU compatibility mode for nested guests","version":1,"mbox":"http://patchwork.ozlabs.org/series/502205/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2230834/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2230834/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=svjj4TBr;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.ibm.com;\n dkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=svjj4TBr; dkim-atps=neutral;\n spf=pass (client-ip=148.163.158.5; helo=mx0b-001b2d01.pphosted.com;\n envelope-from=amachhiw@linux.ibm.com;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.ibm.com","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc\n\t:content-transfer-encoding:date:from:in-reply-to:message-id\n\t:mime-version:references:subject:to; s=pp1; bh=Ubv6yMYn9d//u05u3\n\t4jzNdKgQTaW5W4pj0AddL7IWss=; b=svjj4TBrn4aZkvDbzolMj8YF6qj+ob52Q\n\trsn8OX1ObecoIX8ZIuRbgDBR8X9HZFcU2uYs10qthTT6TqHV5aZwLIISlqIf95QF\n\tl4/LfKU4WArc4cYBOK5GeH8KreujIBBWDbf6qQziafCRsuj2l+fQEDN6fv4vc83V\n\tpMRT7oqT9GoAV/MZHDGo+kKJnBE5O1k8hMfAhfg/lkhVTffEJhnaztl4eKofKuwA\n\t8PyR07wbY2KGy4UGUG+nN9gZLIj9UsWwvMKm9yf7r5BXEq/Fu1K/t/X63QN3fRTZ\n\tus5Yj3qHfe/zq2wt8gRf/E3UfSuzCCVrU17MTiSRl39ihKIGVX6gQ==","From":"Amit Machhiwal ","To":"linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan ","Cc":"Amit Machhiwal ,\n Vaibhav Jain ,\n Nicholas Piggin ,\n Michael Ellerman ,\n \"Christophe Leroy (CS GROUP)\" ,\n kvm@vger.kernel.org, linux-kernel@vger.kernel.org","Subject":"[PATCH 1/6] KVM: PPC: Book3S HV: Validate arch_compat against host\n compatibility mode","Date":"Thu, 30 Apr 2026 11:19:00 +0530","Message-ID":"<20260430054906.94431-2-amachhiw@linux.ibm.com>","X-Mailer":"git-send-email 2.50.1","In-Reply-To":"<20260430054906.94431-1-amachhiw@linux.ibm.com>","References":"<20260430054906.94431-1-amachhiw@linux.ibm.com>","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-TM-AS-GCONF":"00","X-Proofpoint-Reinject":"loops=2 maxloops=12","X-Proofpoint-ORIG-GUID":"zt7r0mqoNlX3WLlD1khd0zPKSRuFFnQa","X-Proofpoint-Spam-Details-Enc":"AW1haW4tMjYwNDMwMDA1NSBTYWx0ZWRfX6OVWkafEfjB8\n mGOxl+gtNffqwNC0wEugg5aIzIDy5P9Eo/9wtpRfGvyESiLF2M5y3Axw/+ZW7aScOwaXXoxAX0C\n 67UhbAH/fqnIStVlf04g4Et9Cr2090B+++Q9UvCU1ErcWuU6SfUhaKk/X91DBO3P+XNyfkYt3ZS\n L0b+ovgMHuZrp5mndhha+k38YvNUds1s4yhs1mPBQVGLiFf3GwdSsHQn57Uf24FGYbeg4yfEn/F\n kq3nRTEV4MNX3LtwXSaZI74+ZPJ+RA4jNhU1vr5xsdbEselicHS0LUwbuyQGzsWmWeJxyLMct8u\n Czx8wB6UGGPGJKPhEBVlAGFTKw80SXvceCALTM79Yc/TqTGHscAaQs8UhiDewJ0fCklHv3mROV7\n vu6ApxZdtiQzoeYFRQ4Mf7djOO38oEdTq8Mbtj71M0tF/sEuCe6N1NLZX4aDxQocQP8xirnGtq7\n WtOyJeHgbivWYO6N1YQ==","X-Authority-Analysis":"v=2.4 cv=VZLH+lp9 c=1 sm=1 tr=0 ts=69f2ed99 cx=c_pps\n a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17\n a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22\n a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=9nGdcix9NZkGgJ1vRr8A:9","X-Proofpoint-GUID":"CQNBagWsl1eIXAex8tZNSm3NPZAAFrRF","X-Proofpoint-Virus-Version":"vendor=baseguard\n engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49\n definitions=2026-04-30_01,2026-04-28_01,2025-10-01_01","X-Proofpoint-Spam-Details":"rule=outbound_notspam policy=outbound score=0\n clxscore=1015 suspectscore=0 adultscore=0 lowpriorityscore=0 phishscore=0\n spamscore=0 malwarescore=0 bulkscore=0 priorityscore=1501 impostorscore=0\n classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0\n reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604300055","X-Spam-Status":"No, score=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tRCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,\n\tSPF_PASS autolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"},"content":"On IBM POWER systems, newer processor generations can operate in\ncompatibility modes corresponding to earlier generations. This becomes\nrelevant for nested virtualization, where nested KVM guests may need to\nrun with a specific processor compatibility level.\n\nCurrently, when running a nested KVM guest (L2) inside a Power11 pSeries\nlogical partition (L1) booted in Power10 compatibility mode, the guest\nfails to boot while setting 'arch_compat'. This happens because the CPU\nclass is derived from the hardware PVR (via mfspr()), which reflects the\nphysical processor generation (Power11), rather than the effective\ncompatibility mode (Power10).\n\nAs a result, userspace may request a Power11 arch_compat for the L2\nguest. However, the L1 partition, running in Power10 compatibility, has\nonly negotiated support up to Power10 with the Power Hypervisor (L0).\nWhen H_SET_STATE is invoked with a Power11 Logical PVR, the hypervisor\nrejects the request, leading to a late guest boot failure:\n\n KVM-NESTEDv2: couldn't set guest wide elements\n [..KVM reg dump..]\n\nThis situation should be detected earlier. Rejecting unsupported\n'arch_compat' values in 'kvmppc_set_arch_compat()' avoids issuing an\ninvalid H_SET_STATE hcall and provides a clearer failure mode.\n\nAdd a check to reject Power11 'arch_compat' requests when the host is\nrunning in Power10 compatibility mode, returning -EINVAL early instead\nof deferring the failure to the hypervisor.\n\nSigned-off-by: Amit Machhiwal \n---\n arch/powerpc/kvm/book3s_hv.c | 6 ++++++\n 1 file changed, 6 insertions(+)","diff":"diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c\nindex 61dbeea317f3..948c6b099a29 100644\n--- a/arch/powerpc/kvm/book3s_hv.c\n+++ b/arch/powerpc/kvm/book3s_hv.c\n@@ -446,7 +446,13 @@ static int kvmppc_set_arch_compat(struct kvm_vcpu *vcpu, u32 arch_compat)\n \t\t\tguest_pcr_bit = PCR_ARCH_300;\n \t\t\tbreak;\n \t\tcase PVR_ARCH_31:\n+\t\t\tguest_pcr_bit = PCR_ARCH_31;\n+\t\t\tbreak;\n \t\tcase PVR_ARCH_31_P11:\n+\t\t\tif ((PVR_ARCH_31 & cur_cpu_spec->pvr_mask) ==\n+\t\t\t\tcur_cpu_spec->pvr_value) {\n+\t\t\t\treturn -EINVAL;\n+\t\t\t}\n \t\t\tguest_pcr_bit = PCR_ARCH_31;\n \t\t\tbreak;\n \t\tdefault:\n","prefixes":["1/6"]}